A Swiss study found that there was a clear improvement in performance and a 30pc increase in concentration after taking Bio-Strath Elixir, which contains yeast and herbal extracts, during a ten-week trial.

It is available from pharmacies, health stores and Tesco Nutricentres, or mail order on 0161 483 1235, priced #11.45 for 250ml.

Energy>

Taking an iron supplement could improve energy levels and boost brain power, and research indicates that iron deficiency in teenagers can result in significantly lower exam scores.

Teenage girls are particularly at risk with nearly 75pc of girls aged 12-19 not receiving their recommended daily intake of iron.

Studies have concluded that reduced iron intake has a detrimental effect on IQ levels and cognitive function.

Spatone Iron, a natural iron-rich spa water is easily absorbed by the body, making it particularly suitable for children. It is available from Boots or by mail order on 01492 640 057, priced #6.49 for 28 sachets.

Stress>

Stress is the most common symptom suffered by youngsters approaching exams, and led to a 50pc increase in calls to ChildLine from pupils struggling to cope with exam tension last year.

Carly Harding, a Bach Foundation registered practitioner, says: "Stress causes butterflies in the stomach, feelings of nausea, loss of appetite which can be very disturbing and exhausting. It can literally make your mind go blank so you don't feel as though any information is being absorbed."

She advises two quick sprays of Bach Rescue Remedy on the tongue to restore calm and focus. "It's totally natural and non-drowsy so it's safe to take as often as needed during revision time and during the exam itself."

Available from Boots, health food and grocery stores nationwide, priced #3.95 for 10ml.

Sleep>

Anxiety about exams can cause insomnia, but sleep is vital to refresh the mind and body, and ensure sufficient supplies of the chemical that controls energy, motivation and intelligence.

Healthy serotonin levels ensure deep restful sleep - to top them up you need lots of foods such as turkey, bananas, milk, cheese and beans.

These are rich in amino acid, which the body turns into serotonin.

Natural supplement Cellfood also contains tryptophan, as well as other essential amino acids.